For those of you that have tried making your own creams, lotions, sunscreens or liquid foundation (to name but a few) you will empathise with me when I say that emulsions can be scary things.  Armed with a bullet proof knowledge that oil and water don’t mix without help  we  ready ourselves with an emulsifier or two  (the help) a good mixer  and a strong cup of tea (essential) and prepare to beat our proposed dispersed phase into a neat and orderly submission. Only our cunning plans don’t always work. Do they?

There are many ways for an emulsion to leave you crying and unfortunately your choice of emulsifier/ emulsifier combo is only the beginning.  I’m  talking about Stokes Law….

Yes it does look rather scary at first but once you become familiar with all the V’s, d’s, g’s and triangles the world becomes a much brighter place!

Now, before we go any further we should re-introduce ourselves to a few features of an emulsion.  As we are just learning we will pretend that emulsions are simple things with only two possible options – oil in water or water in oil.  Us science people like to think of an emulsion as two phases – the continuous phase (the bulky bit that the other drops sit inside of) and the dispersed phase (the small bubbles that float around inside the continuous phase).   When you have oil as the continuous phase you have a water-in-oil emulsion and when you have water as the continuous phase you have oil-in-water.  The most common is oil-in-water as these are cheaper, feel lighter and are generally suitable for most applications.

So, V  = velocity. This is the speed  at which your tricky little […]